Insulated conducting member and method of applying the insulation



ULATION 2 Sheets-$heet l G. CAMILLI File'd June 16, 1942 July 2, 1946.

INSULATED CONDUCTING MEMBER AND yMETHOD APPLYING THE INS l !p |.f| n

Inventor: Guglielmo' Camilli,

Hls Attorney.

July 2, 1946- G. cAM|LL| a 2,403,340`

INSULATED CONDUCTING MEMBER AND METHOD OF APPLYING THE INSULATION Filed June 1e, 1942 2 snetssheet 2 ooouooouoooqo ooooooooooooo o ooo oo ooo ooo non gooooooo' onooo ooooooo Inventor; Guglielmo Camlli,

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Patented July 2, 1946 www misurarsi) coNDUo'nNG MEMBER AND METHOD or Arx-smo. 'rma msnm- TON ,Gugiieimo camini, mussels, Mm, animar to General Electric Company, a corporation of New York Application June 16, 1842, Serial No. 447,220

iol. 175-2'1) 6 laims. l

My invention relates to electrical insulation, and to an improved method of applying the insulating material to an electrically conducting article, and to the article which is so insulated.l

Heretofore, it has been common practice when applying high voltage insulation to a conducting article such as some coils, to apply a suitable tape, such as crepe paper, by taping the coil by hand. Such a procedure is a relatively costly and tedious operation, and an improved arrangement for hydraulically applying an insulating covering to an electrically conducting article, such as a coil, at o. relatively rapidrate, is described and claimed in a copending application, S. N. 326,042 of Camilli, Hemphill and Endicott, iiled Maron 26, i940, and assigned to the same assignee as this present invention, and which issued on July 2l, i942 as Patent No. 2,290,67i.

It is, therefore, an object of my invention to provide an improved method oi' the type described and claimed in the alcove-mentioned application for electrically insulating a conducting member.

Another object oi my invention is to provide a conducting member with an improved composite insulating covering.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will he pointed out with porticularity in theclaims annexed to and iorming a part of this specification.

In the drawings: y

Fie, l diagrammatically iliustrates apparatus which may be employed to apply the insulated covering: Fig. 2 is a. side elevation in partial section of a winding having one covering oi my improved composite insuiation; Fig. 3 is a side view of a spacer arrangement which is employed to produce my improved composite covering; Fig. Li is a sectional side eier/ation taken along the lines tof Fig. 3; Fig. ii is a side elle` vation, in partial section, of the winding of Fig. 2, after a second covering of my composite insulation has been applied; Fig. 6 is fragmentary sectional side elevation illustrating e. modified arrangement oi employing my improved screen; Flo. l is a side view oi the screen employed in Fig. ii and which screen is a modieaticnoi the screen shown in Figs. :i andi, and Fig. 8 is a side view partially in section illustrating a transformer having my improved insulated. windings.

The improved method described in the abovementioned copending application or insulating an electrically ccnductini: article, such as e coil winding, includes the steps of placing a permeable screen around the article to be coated and spacing the screen from the article to provide a fluid channel. 'Ihe article is then placed in a bath including a fluid having finely divided particles or bits oi insulating material suspended therein. 'A difference of pressure is produced between the fluid inside and outside the' screening so that the fluid may pass through the screen and deposit its suspension. The thickness of a covering which may be so deposited may, or course, be dependent on such factors as the relative values of ypressure between that inside and outside of the screen, the sire of the insuiating particles suspended in the duid, and the type or ud. Furthermore', as

the insulating covering builds up, the fluid which deposits its suspension must pass through the already deposited insuiation, so that a pressure drop `will obtain through the covering which has allready' heen applied. Assuming constant condi tions, therefore, o point "will ice reached when no further duid willi pass through the already de posited insulating covering so that no further insulation will he deposited.

Referring to the drawings, in Fig. l I have illustrate-d an apparatus in which my invention he carried out, but it is to Ice understood that any other suitable apparatus may loe employed.

This apparatus, which is described in the aboveu mentioned copending application, includes a tank i8 which is provided with a suitable pressure tight cover il. In this tank placed a suitable fluid, such as s. liquid is which has suspended therein the material which is to he coated upon an article i3. Any suitable insulating rnateriai may be used,

it being only necessary to use one which when .beaten or broken into hits will have such characteristics that it will not pass in appreciable amounts through a suitable perforated or screen member. Examples oi suitable materials are mica and suchflbrous materials as paper and asbestos. Howeven'it is to he understood that other materials which may he hrolren into particles, or fibers, or bits of proper size may also be applied according to this method. When applying the method to a high voltage coil, a cellulosic material such as kraft paper, produces an eflicient insulating covering. Such. paper ordinarily comes from the mills in thick sheets so that it is necessary to get the paper in proper condition so that it may be hydraulically applied. This paper is, therefore, broken into particles or bits so that it becomes a mass ofiibrous material which may be mixed with a. liquid, such as water. In order to thoroughly hydrate the paper it may be beaten while in water so that it becomes a wet mash. This pulp may then be placed into a tank I4 which leads to the tank III through a piping system I5. In order to proportion properly the amount of liquid with the pulp there may be provided an intake pipe I8 in the tank IU for the liquid. In order to obtain the desired amount of mixture I2 of liquid and paper pulp in the tank I0, a measured amount of pulp'is caused to flow into the tank I by opening a valve member i1 and forcing it under suitable pressure such as air or water pressure which may be applied through a pipe Ila. Water is then allowed to flow into the tank by opening a control valve i8. Any suitable proportion of paper pulp to water may be used, such \as about one part of paper pulp by weight to 99 parts of water, when a screen of about 200 mesh is employed.

The article to be insulated as shown in Fig. 1

includes a high voltage coil winding for an electric induction apparatus, such as a transformer which includes turns Il which may be covered with a suitable permeable envelope or screen of any suitable material 20. which has at least a portion thereof spaced from the winding or from a portion of the turns Il so as to provide a suitable fluid channel arrangement In order to produce a difference in pressure Abetween the liquid inside the screen 20 and that surrounding the screen. water pressure may be applied to the tank Il through the pipe I6. Excess water may be drawn oil' through a pipe 2i having a, valve 22. A pressure differential between that inside and outside the screen may also be provided through a suitable pumping ar` rangement which may be connected to the screen member 20 through a pipe member 23. 'I'his pipe member is in turn connected through a pipe system 24 to a sump 25, the sump being connected to a pump through a pipe 26. Thus, it will be seen that if water pressure is applied by opening the valve Il and the pump attached to the pipe 2l is operated, the water adjacent the screen member 20 will now through the i screen and pass out through the channel arrangement 20', and pipe 2|. Instead of using both pressure and vacuum, either may be used separately. As described in the above-mentioned application, this movement will cause suspended particles or bits in the water to be deposited on the outside surface of the screen or perforated member 20. Any suitable pressure differential may be developed depending upon the thickness and type of hydraulically applied coating which is desired. During the coating operation, since water is constantly entering and leaving the tank Il, a. proper proportion of liquid and pulp may be kept by constantly introducing pulp into the tank Il through the pipe il at a suitable rate. Assuming constant pressure conditions, the coating will continue to build up to a thickness until the fluid stops flowing through the covering which has already been deposited. After the coil has been removed a hydraulically applied coating 21. as shown in Fig. 2, will cover the outside surface of the screen 20.

In hydraulically applying an insulating covering to a coil in the manner described above, I have found that after a Vpredetermined time under a given set of conditions during which the insulating bits are deposited, the particles which are then applied will not adhere sufficiently to the already i applied covering. This covering which is -applied .after this predetermined time may fall on while the coil is being removed from the bath, or if it remains, the insulation will be of an inferior quality. It appears that this is due to the fact that after a predetermined thickness has been built up for a given set of conditions, the fluid passes through the already applied insulatingcovering at such a low rate that bits deposited by this slowly moving uid do not adhere sufficiently to the already applied insulating covering. Therefore, when it is desired to apply an insulating covering of a greater thickness than that which obtains before the rate of flow of the carrying fluid drops below a predetermined value, (which predetermined rate may be determined by experiment for any given set of conditions) the coil may be removed from the bath while the fluid is still flowing through the already deposited insulation at a sumcient rate to produce a relatively tight covering; a second screen arrangement may then be applied over the already applied insulating covering 21 and another hydraulically applied coating produced on the outside surface of the second screen. Thus, the coil is removed before that time when the fluid stops all flow through the already deposited insulation and, of course, the coil may be actually physically removed at this predetermined time, that is, when the rate of flow drops to a predetermined value, after turning off the vacuum and pressure and removing the cover il from the tank I0. Therefore, in describing that the coil is removed from the bath while the fluid is still flowing through the already deposited insulation at a sufficient rate to produce a relatively tight covering is, of course, meant that the coil is removed at that predetermined time in any suitable manner, such as upon turning oif the means for creating the higher pressure in the fluid surrounding the envelope.

In Fig. 3 I have illustrated a suitable `screening arrangement ID which may Abe applied over the insulation 21 in any suitable manner such as by taping it around the outside surface. The tape 30 forming the spacer portion of the screen may be of any suitable material, suchas Vcellulose acetate with a plurality of protrusions Il extending therefrom. These protrusions may be formed in any suitable manner such as by passing a fiat piece of cellulose acetate tape over a pair of hot rollers, one of which has outwardly extending portions and the other cooperatively receiving indentations which expands portions of the tape to provide the protrusions Il. The tape may, therefore, be applied over the insulation 21 with the' protrusions extending outwardly as is illustrated in Fig. 5. A screen arrangement 32 of any suitable type such as cloth may then be applied over` the tape Il, and a plurality of protrusions 3i will space the screen from the tape 30 providing a fluid channel arrangement 3l similar to the channel arrangement 20'.

` pipe 2l may then be connected to this channel arrangement and the article then placed in the bath of Fig. 1 and a second coating Il produced thereon in the manner which has already been described.

It will be seen in Fig. 3 that the tape III has a plurality of openings or perforations 8l. Thus. when the coil is placed in a suitable casing 3l as illustrated in Fig. 8 and impregnated with a suitable insulating fluid, this iluid may permeate through the various composite layers through the perforations II of the screen portion Il.

In Fig. 8 I have illustrated a Spacer arrangement l1 around the covering 21, the spacer, as illustrated in' Fis. 7. having a plurality of proi a hydraulically applied trusionsl; the tape being so wound that the protrusions extend inwardly adjacent the covering 21. The tape 31 is perforated with sufli.

ciently small openings that when the so taped article is placedin the bath the bits of insulating material will not pass in appreciable amounts through the screen 37.

Although I have shown and described particular embodiments of my inventionj do not desire to vbe limited to the particular embodiments -described. and I intend in the appended claims to hydraulically applied insulating material sur-r rounding and closely tting said screen, said screen having a fluid passage connected to said channel through which a fluid may pass during application of said hydraulically applied insulating material, means surrounding said hydraulically applied insulation providing 'a second screen, integral protrusions extending from said second screen means to space said screen means from said insulation and provide-a channel, and

insulating material surthat it is practicable to deposit, hydraulically, the

rounding and closely fitting said second screen means.

2. An insulated coil winding 'for an electric apparatus including a conductor turn, screen means permeable to a iiuid surrounding said conductor turn, means spacing at least a portion of said screen from said turn inA order to form a fluid channel between said turn and said screen.-

a hydraulically applied insulating material surrounding and closely fitting said screen, said` outwardly extending integral protrusions for spacing said second screeny means from said insulation, and a hydraulically applied insulating material surrounding and closely fitting said second screen, said flexible sheet means being perforated so that an impregnating iiuid Afor said coil may permeate said insulating covering o through the iiexible sheet me N18. 3. -An insulated electrical conductor comprising, in combinations plurality of superposed layers of insulation surrounding said conductor,`

" 4rated layer. stopping 'out of said channels 6 and perforated spacing means separating sa layers from each other and separating the innermost layer from said conductor, said spacing means which are between said layers havingintegral fluid conducting channels, said layers comprising relatively tightly matted insulating fibers hydraulically deposited on the cuter surface of the respective perforated sping means, each layer being substantially of the maximum thickness consistent with tight matting of the fibers total thickness of all the layers being substantiallygreater than the maximum thickness to which it is possible to deposit, a single layer regardless of tightness of matting of the fibers.

4. A conductor coil having a predetermined amount of surrounding solid insulation, a layer of perforated insulation mounted on said solid insulation and in direct'contact therewith, said perforated layer including a plurality of channels extending generally parallel to the surface of said solid insulation, and a homogeneous layer of tightly matted iibrous insulation hydraulically deposited on said layer of perforated insulation.

5. 'Ihe method of hydraulicallyl depositing tightly matted multi-layer brous insulation` to any desired thickness on an electricalv device including the steps of wrapping a channelled and perforated layer of insulation on top of and inv contact with an underlayer of insulation, submerging said device in fibrous insulation held in suspension, causing said liquid to flow through .said perforations and out of said channels at a predetermined rate so as to" deposit said fibers on said perforated layer, stop-v ping said flow when a predetermined thickness of deposit has been built up. and repeating said steps until the' desired total thickness of tightly matted insulation is deposited.

6. The method of hydraulically depositing 4tightly .matted multi-layer fibrous insulation to anydesired thickness on an electrical device including the steps of wrapping a channelled and perforated layer of insulation on top of and in contact with an under layer of insulation, submerging said device in a liquid bath having fibrous insulation held in suspension, causing said liquid to flow through said perforations and at a predetermined initial rate so las to deposit said fibers on said perfofore the maximum thickness of deposit has been built up and while the outer surface of said'deposit is relatively tightly matted, and repeating said steps until the desired total thickness of ltightly mattedinsulation is deposited.

GUGLIELMO cAMnm. I

integral a liquid bath having vsaid iiow substantially be- 

